密度对稻茬晚播小麦^(15)N积累、分配与利用特征的影响

Effects of density on characteristics of ^(15)N accumulation,distribution and utilization of late-sowing wheat in rice-wheat rotation

通过^(15)N微区试验,研究晚播条件下不同密度小麦氮素吸收与利用的差异,探索提高晚播小麦氮素利用效率的生理机制。结果表明:稻茬晚播小麦开花期植株吸收的氮素67%~71%、成熟期植株吸收的氮素53%~70%来自土壤中氮素,^(15)N微区试验结果表明开花期植株对肥料^(15)N的吸收以基施^(15)N为主,成熟期吸收追施^(15)N比例则高于基施^(15)N。花后营养器官中的肥料^(15)N向籽粒中转运,其中茎鞘转移量最大,转移氮素以基施^(15)N为主。增加密度可显著增加成熟期植株对追肥中肥料^(15)N的吸收量及占总氮比例。高密度条件下籽粒中氮素的积累提高,主要是增加营养器官中追肥^(15)N向籽粒中转运。这说明晚播条件下适度增加密度有利于提高植株对肥料氮的吸收,减少土壤中肥料残留,提高营养器官中氮素向籽粒中的运转量,结合氮肥后移措施有利于提高氮素利用率。

In order to improve nitrogen uptake and use efficiency, and the yield potential of late-sowing wheat, the ^(15)N micro-zone test at different density were used to study the differences in nitrogen absorption and utilization at different density of late-sowing wheat, and the physiological mechanisms for increasing nitrogen use efficiency in late-sowing wheat were explored. The results showed that: in late wheat sowing, wheat plants absorbed 67%-71% of nitrogen during flowering and 53%-70% of soil nitrogen was absorbed during maturity. Nitrogen fertilization results indicated that ^(15)N uptake during the flowering stage was mainly from basal ^(15)N, while in mature stage, the proportion of topdressing ^(15)N was higher than that of basal ^(15)N.^(15)N in vegetative organs after anthesis was transported into grains, with the largest amount transferred from stem and sheath, and basal ^(15)N was the main nitrogen source. The increased density significantly increased the uptake of ^(15)N from topdressing and the proportion of total nitrogen. At the same time, the accumulation of nitrogen in grain increased under high-density conditions, mainly due to the increase of the transport of topdressing ^(15)N into grains in vegetative organs. Our study indicated that moderately increasing density under late sowing conditions was beneficial to increase nitrogen uptake by plants, reduce fertilizer residues in soil, and increase the transferring of nitrogen in vegetative organs to grains. Late topdreassed nitrogen will improve the nitrogen utilization rate.